Inkjet cartridges are now well known in the art and generally comprise a body containing an ink supply and having electrically conductive interconnect pads thereon and a printhead for ejecting ink through numerous nozzles. In thermally activated inkjet cartridges, each cartridge has heater circuits and resistors which are energised via electrical signals sent through the interconnect pads on the cartridge. Each inkjet printer typically has a plurality, normally four, of cartridges each one having a different colour ink supply for example black, magenta, cyan and yellow, removably mounted in a carriage which scans backwards and forwards across a print medium, for example paper, in successive swaths. When the scanning carriage correctly positions one of the cartridges over a given location on the print medium, a jet of ink is ejected from a nozzle to provide a pixel of ink at a precisely defined location. The mosaic of pixels thus created provides a desired composite image.
The cartridges must thus be held within the scanning carriage of the printer very precisely, so that their position over the print media is accurately known. This is normally achieved by utilising a cartridge holder, forming part of the scanning carriage, which has a number of biasing means for biasing datums on the cartridge against datums on the cartridge holder, see for example U.S. Pat. No. 5,642,143. Furthermore reliable and repeatable electrical contact must be made between the printer and the cartridge, via the carriage. Generally, a flexible insulating tape having electrically conductive pads (also known as a flex circuit) is attached to the cartridge holder and this is arranged so that the electrically conductive interconnect pads on a cartridge make contact with the pads on the flex circuit when the cartridge is inserted into the carriage of the printer, as described for example in U.S. Pat. No. 5,461,482.
Inkjet cartridges are increasingly becoming more sophisticated and complex in their construction and longer lifetimes are also required of cartridges, particularly those for use with printers having an off-carriage ink reservoir which replenishes the cartridge's ink supply. This has lead to greater sophistication in the so-called "servicing" of cartridges by a printer. It is normal for printers to have a service station at which various functions are performed on the cartridges while they are mounted in the printer carriage such as wiping, spitting and capping, see for example U.S. Pat. No. 5,585,826. Wiping comprises moving a wiper of a specified material across the printhead of a cartridge to remove paper dust, ink spray and the like from the nozzle plate of the printhead. Spitting, ejecting ink into a spittoon in the service station, is performed to prevent ink in nozzles which have not been fired for some time from drying and crusting. Cartridges are capped by precisely moving the carriage, and often the cap too, within the service station, so that the cap mates with the printhead and forms a seal around the nozzle plate. Capping prevents ink on the printhead and in the nozzles from drying by providing the correct atmosphere around these components and thus reduces the risk of crusting and ink plug formation in the nozzles. Often, each cartridge will have its own servicing components, for example wiper and cap, within the service station so that contamination of these components for example by different coloured inks does not occur. These servicing components are also often replaceable, either individually or as a unit, so that they can be changed during the lifetime of the printer, or even (given presently achieved longer cartridge lifetimes) when the cartridge is replaced, so as to maintain high quality cartridge servicing functions within the printer.
This same degree of care in maintaining the functionality of inkjet cartridges when mounted in the carriage of a printer has not been applied to the design of storage containers, also known as garages, for storing inkjet cartridges when removed from an inkjet printer carriage. There are a number of circumstances when there is a requirement for removing a partially used cartridge from a printer for storage, for example to utilise a colour cartridge instead of a black one in single cartridge printers, to replace a cartridge or cartridges for printing text by ones for printing photographic images, or by ones containing specialised ink, for example ink that is resistant to deterioration by ultra-violet light. Despite these requirements, cartridge garages have remained relatively unsophisticated. Prior art cartridge garages comprise a compartment for storing a single cartridge and a permanent cap for capping the cartridge. An example of a prior art cartridge garage is shown in FIG. 1. This garage is sold under part number C2621-60007 by Hewlett-Packard and is intended for the storage of cartridges used with Hewlett-Packard's Portable DeskJet 310 inkjet printer. The garage may store one of either a black inkjet cartridge 1 or a colour inkjet cartridge 2 and has two permanent caps (not shown) mounted at the base of the garage which are not designed to be removed by the user. The garage also has two springclips 3 and 4 for respectively retaining one of either the black 1 or colour 2 cartridge.